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eb39fafa4f
includes a (minimal) working wrapper Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
124 lines
2.7 KiB
Markdown
124 lines
2.7 KiB
Markdown
# Disallow Labeled Statements (no-labels)
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Labeled statements in JavaScript are used in conjunction with `break` and `continue` to control flow around multiple loops. For example:
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```js
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outer:
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while (true) {
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while (true) {
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break outer;
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}
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}
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```
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The `break outer` statement ensures that this code will not result in an infinite loop because control is returned to the next statement after the `outer` label was applied. If this statement was changed to be just `break`, control would flow back to the outer `while` statement and an infinite loop would result.
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While convenient in some cases, labels tend to be used only rarely and are frowned upon by some as a remedial form of flow control that is more error prone and harder to understand.
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## Rule Details
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This rule aims to eliminate the use of labeled statements in JavaScript. It will warn whenever a labeled statement is encountered and whenever `break` or `continue` are used with a label.
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Examples of **incorrect** code for this rule:
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```js
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/*eslint no-labels: "error"*/
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label:
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while(true) {
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// ...
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}
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label:
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while(true) {
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break label;
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}
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label:
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while(true) {
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continue label;
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}
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label:
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switch (a) {
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case 0:
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break label;
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}
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label:
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{
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break label;
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}
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label:
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if (a) {
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break label;
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}
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```
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Examples of **correct** code for this rule:
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```js
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/*eslint no-labels: "error"*/
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var f = {
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label: "foo"
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};
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while (true) {
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break;
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}
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while (true) {
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continue;
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}
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```
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## Options
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The options allow labels with loop or switch statements:
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* `"allowLoop"` (`boolean`, default is `false`) - If this option was set `true`, this rule ignores labels which are sticking to loop statements.
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* `"allowSwitch"` (`boolean`, default is `false`) - If this option was set `true`, this rule ignores labels which are sticking to switch statements.
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Actually labeled statements in JavaScript can be used with other than loop and switch statements.
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However, this way is ultra rare, not well-known, so this would be confusing developers.
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### allowLoop
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Examples of **correct** code for the `{ "allowLoop": true }` option:
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```js
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/*eslint no-labels: ["error", { "allowLoop": true }]*/
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label:
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while (true) {
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break label;
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}
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```
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### allowSwitch
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Examples of **correct** code for the `{ "allowSwitch": true }` option:
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```js
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/*eslint no-labels: ["error", { "allowSwitch": true }]*/
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label:
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switch (a) {
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case 0:
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break label;
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}
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```
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## When Not To Use It
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If you need to use labeled statements everywhere, then you can safely disable this rule.
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## Related Rules
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* [no-extra-label](./no-extra-label.md)
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* [no-label-var](./no-label-var.md)
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* [no-unused-labels](./no-unused-labels.md)
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